Mares come into heat during the spring when there is more light. During the spring and summer, a mare comes into heat approximately every 3 weeks. If you have a breeding mare or your mare has come into contact with a stallion during her heat cycle, you may want to determine if she is pregnant. The gestation period, or time a horse carries a baby, is 11 months, and mares do not begin to look round in the stomach until the last 3 months of pregnancy. This guideline provides instructions for checking mares for pregnancy.

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Steps

Method 1 of 2: Non-chemical Methods to Check Mares for Pregnancy

1

Put your mare in with a stallion around 14 days after they have been covered (bred) with a stallion. When you are checking mares for pregnancy, their behavior toward the stallion may change. If they are pregnant, they will ignore the stallion's attention.

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2

Watch your breeding mare for signs of heat. Some mares raise their tails, squirt, and become difficult during their heat cycles. If the mare goes into heat 21 days after a stallion has serviced her, she is not pregnant.

3

Call your vet when checking mares for pregnancy, and have them come out to perform a transrectal palpation 16 to 19 days after the mare has been with a stallion.

The vet will insert a hand into the mare's rectum and inspect the uterus for pregnancy signs.

A pregnant mare's uterus will change shape and tone.

4

Have an ultrasound done on your mare 55 to 70 days after she has been with a stallion. An ultrasound is a non-evasive method when checking mares for pregnancy.

The ultrasound uses sound waves to create a picture of the uterus and can monitor the heartbeat of a fetus.

If you do not have an ultrasound machine, you will have to call the vet. This procedure may be expensive.

Method 2 of 2: Chemical Methods to Check Mares for Pregnancy

1

Check your breeding mare's blood for signs of pregnancy with a blood test. A pregnant mare's hormone levels will change, and this will show up in her blood.

Have your vet come out to take a blood sample. Your vet will send the blood sample to a laboratory and have it tested.

Test the level of pregnant mare serum gonadotropin (PMSG) 40 to 100 days after your mare has been with a stallion. If your mare was pregnant but lost the fetus, the PMSG test may give inaccurate results.

Analyze the level of oestrone sulphate 100 days after the breeding. Oestrone sulphate levels increase with the presence of a foal, but go back to normal if the fetus is aborted.

2

Give your breeding mare a urine test. When checking mares for pregnancy, oestrone sulphate can be found in the mare's urine.

Obtain a home pregnancy testing kit from a feed store or online.

Test your breeding mare's urine 110 to 300 days after they have been with a stallion.

Cut a 1 gallon (3.8 L) or 2-liter liquid container in half with a knife. Use the bottom to collect your mare's urine.

Follow the directions on the pregnancy test kit to analyze your mare's urine. It takes 10 minutes to obtain the results.

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Horse owners often opt to have a vet perform the initial pregnancy test to determine if the pregnant mare is carrying twins. Having twins may be dangerous for your horse.

Breeding mares sometimes slip, or miscarry, the foal within the first 100 days of pregnancy. A home pregnancy kit is an inexpensive method to perform a second pregnancy test after the initial 100 days.